The World Federation One Stop Fiqh

Ruling 435

It is possible for a pregnant woman and for a breastfeeding woman to menstruate. The ruling of a pregnant woman and a non-pregnant woman is the same, except that if a pregnant woman who has the habit of time47 experiences bleeding with the attributes of ḥayḍ after the passing of twenty days from the first day of her habit, it is necessary for her, based on obligatory precaution, to do the things that a mustaḥāḍah must do and refrain from doing the things that are unlawful for a ḥāʾiḍ to do.

47 This is explained in Ruling 468.